1. Field of the Invention
The present invention relates to an apparatus for measuring a displacement characteristic of a workpiece when a certain physical quantity is applied to the workpiece.
2. Discussion of the Prior Art
In some fields of technology, there is a need to measure or detect a characteristic of displacement of a given material or workpiece which occurs due to a certain physical quantity applied thereto. For instance, it is necessary to measure a hysteresis characteristic of displacement of the workpiece, or a transient response of the workpiece to the physical quantity. For inspecting the quality of a piezoelectric element, for example, it is desired to easily test or inspect the element for the hysteresis characteristic or transient response.
One conventional method for testing the piezoelectric element uses a strain gauge for detecting a variation in the amount of displacement of the element with a change in a voltage applied thereto.
However, the conventionally used strain gauge has a maximum resolution of as low as a few or several microns (.mu.m). To induce a displacement of the piezoelectric element larger than the maximum resolution, a voltage of several tens to several thousands of volts must be applied to the element. In the case of the piezoelectric element consisting of a thin film, the film tends to easily suffer from dielectric breakdown or puncture of insulation. This makes it difficult and cumbersome to detect the displacement of the piezoelectric film.